Question

1. What are three ways in which vesicles in a cell are moved using directed motion.

2. What is the average size of a myosin motor step along an actin filament in nm)? What is the average size of a kinesin motor step along / (across) a tubulin dimer (in nm)?

3. Write the definition of the rate of ATP hydrolyzation Rin your own words. How would you calculate the rate of ATP hydrolyzation, you know the step size of the motor proteins and the average vesicle velocity. Write the equation here.

4.Use the equation from Question 3 and your answer to Question 2 to calculate the rate of ATP hydrolyzation, R. For step size, assume the vesicle is being transported by a myosin motor protein. (Hint: make sure you convert values to the appropriate units) The units for rate of ATP hydrolysis are s^-1

Answer 1

Que-1: 1. What are three ways in which vesicles in a cell are moved using directed motion ?

The plasma membrane is the significant protective phospholipid layer located around the cells and mediates the movement of molecules between the cells. Phagocytosis and exocytosis are vesicle-mediated processes that occur in relation to the cell membrane. The plasma membrane mediates the transport of molecules through facilitated diffusion or passive transport or active transport. Carrier proteins and other membrane proteins mediate this transport process based on the concentration gradient.

The transport of larger molecules or other substances into the cell by means of transport vesicles is known as endocytosis. It occurs by three mechanisms namely pinocytosis, phagocytosis, and receptor-mediated endocytosis.

In receptor-mediated endocytosis, the extracellular molecules will bind to the receptor molecules finally cause ‘invagination’ in the plasma membrane. Thus, the Golgi vesicles with ‘carrier molecules’ bound to the plasma membrane. For example, the bad cholesterol uptake by the liver from the blood is an example of receptor-mediated endocytosis to remove bad cholesterol. Thus, the atherosclerotic plaque formation can be reduced and the risk of cardiac disease (angina and myocardial infarction) is reduced.

Phagocytosis (or cell eating) happen similar to pinocytosis, but the solid particles enter into the cell through this process than the liquids. Phagocytes (a type of white blood cell) engulf bacteria and other cell debris by this phagocytosis process.

Pinocytosis (or cell drinking) is a process, in which small droplets outside the cell are taken in by means of a small tube-like structure formed from the cell membrane. As the droplet enters into the structure, the tube seals and detaches from the cell membrane. This sac then enters into the cytoplasm. Cells take proteins and other substances in this way, which cannot pass through the cell membrane.